Chemical sensitizing of emulsions



Patented July 10, 1945 UNITED STATES PATENT OFFICE 2,380,280 CHEMICALssssrnzmc or EMULSIONS No Drawing. Application March 6, 1943, Serial No.478,303

12 Claims.

appreciably increasing the optical range of sensitization. Agent usedfor this purpose have consisted for the most part in compounds ofelements of the sulfur group and bio-chemica1 extracts. The presentinvention relates to a new class oi.

compounds for the purpose of increasing the speed of photographicemulsions.

I have found that photographic emulsions of the silver halide type maybe treated with watersoluble salts of unsaturated lower aliphatic acidsfor the purpose of increasing the speed or sensitivity,

Compounds suitable for this purpose are the water-soluble salts ofunsaturated lower aliphatic acids. These include monobasic acids such asacrylic acid, methacrylic acid, benzoyl acrylic acid, furoyl acrylicacid and crotonic acid, and dibasic acids such as itaconlc acid,citraconic acid, and maleic acid. Water-soluble salts of these acidswhich may be employed are the sodium, potassium and ammonium salts.

The degree of increase in sensitivity obtained has been found to varywith the type of emulsion employed and with the nature and quantity ofsalt added. I'he addition agents of my invention may be employed withnon-optically sensitized gelatino-silver halide emulsions or withemulsions sensitized with optical sensitizing dyes in the customarymanner. In some instances the increase' in speed of the emulsion wasaccompanied by a.

change in contrast as well, while in other cases little or no change incontrast was noted.

Suitable compounds for increasing the speed of silver halide emulsionsaccording to my invention are the folowing:

CHFCHC 0 ONa Sodium acrylate CH: CHF=(B-C O 0 Na Sodium metbacrylatecmon==cnc 0 om Sodium crotonste C;H |C 0 GE -CHIC O 0N:-v Sodiumbenzoylacrylstc cH-CH H Hl-GH=CHCOON3 a-iuryl sodium acrylste CH:=C-Cv0ONa Hr-C 0 ON a Sodium itoconetc C Hr-C C O 0 Na 0 H-0 0 O Na Sodiumcitraconate C 11-0 0 O Na (EH-C O ONa Sodium maleate My invention willbe illustrated by reference to the following specific examples, in whichthe speed is expressed as ten times the reciprocal of 35 the inertia.

Example 1 lar emulsion to which had been added 10 grams per liter ofemulsion of sodium acrylate. The emulsion to which the sodium acrylatehad been added showed a sensitivity increase of about 60% without anappreciable increase in the gamma or fog level. The emulsions comparedas follows:

lllji Gamma Fog Speed lllrckfln .H. 575 1.29 .06 Emulsion with log.sodium ucrylatezlitor I 020 1.55 .07

Both emulsions were developed for 4 minutes in the following developingsolution:

Monomethyl-p-aminophenol sulfate grams 2.2 Hydroquinone do 8.8 Sodiumsulfite (desiccated) do 96 Sodium carbonate (desiccated) do 48 Potassiumbromide dO 5 Water to liter 1 Example 2 A high speed opticallysensitized emulsion of medium fine grain having a speed of 1320, a gammaof 0.74 and a fog level of 0.05 was compared with similar emulsions inwhich sodium acrylate and sodium methacrylate had been added in theamount of grams per liter of emulsions. A speed increase was noted asshown in the following table:

10/i Gamma Fog Check Emulsion with 10 g. sodium acryIate/hter. Emulsionwith 10 g. sodium methacrylate/liter.

The emulsions were developed for 12 minutes in the following developingsolution:

I Monomethyl-p-aminophenol sulfate grams 2 Hydroquinone do 5 Sodiumsulfite (desiccated) do 100 Borax do 2 Water to liter 1 Example 3 Anoptically sensitized gelatino-silver bromide emulsion having a speed of1150, a gamma of 0.74

and a fog level of 0.05 was compared with a similar emulsion to which 5grams of sodium methacrylate had been added per liter of emulsion. Theresults are shown inthe following table:

w/i Gamma speed Fog (heck .Q Emulsion with 5 g. sodium methucrylnte/liter tained depends upon the quantity of the addition agent used. Withthese agents the speed increase varies from 25% to or more dependingupon the'type of emulsion and the nature and quantity of the salt added.

While my addition agents will generally be used with gelatino-silverhalide emulsions, such as emulsions of the bromide or bromo-iodide type,they may also be used with silver halide emulsions in which the carrieris aibumcn, collodion or other cellulose ester or synthetic resin,provided that there is considerable water in the emulsion to act as asolvent for the addition agent.

It will be understood that the above examples are illustrative only andthat my invention is to be taken as limited only by the scope of theappended claims.

I claim:

l. The method of increasing the speed of a silver halide photographicemulsion, which comprises adding thereto from 5 to 25 grams per liter ofa water-soluble salt of an unsaturated, lower aliphatic acid.

2. The method'of increasing the speed of a silver halide photographicemulsion, which comprises adding thereto from 5 to 25 grams per liter ofthe sodium salt of an unsaturated, lower alipliatic acid.

3. The method of increasing the speed of a silver halide photographicemulsion, which comprises adding thereto from 5 to 25 grams per liter ofa water-soluble salt of an unsaturated, lower aliphatic acid.

4. The method of increasing the speed of a silver halide photographicemulsion, which comprises adding thereto from 5 to 25 grams per liter ofthe sodium salt of an acrylic acid.

5. The method of increasing thespeed of a gelatino-silver halideemulsion, which comprises adding thereto the sodium salt of acrylic acidin an amount sufficient to effect an appreciable sensitivity increase.

6. The method of increasing the speed of a gelatino-silver halideemulsion, which comprises adding thereto the sodium salt of methacrylicacid in an amount suflicient to eifect an appreciable sensitivitincrease.

7. A gelatino-silver halide emulsion containing as a speed-increasingagent from 5 to 25 grams per liter of a water-soluble salt of anunsaturated. lower aliphatic acid.

8. A gelatino-silver halide emulsion containing as a speed-increasingagent from 5 to 25 grams per liter of the sodium salt of an unsaturated,lower monobasic acid.

9. A gelatino-silver halide emulsion containing as a speed-increasingagent from 5 to 25 grams per liter of the sodium salt of an acrylicacid.

10. A gelatino-silver halide emulsion containing as a speed-increasingagent from 5 to 25 grams per liter of the sodium salt of acrylic acid.

11. A gelatino-silver halide emulsion containing as a speed-increasingagent approximately 10 grams per liter acrylate.

12. A gelatino-silver halide emulsion containing as a speed-increasingagent approximately 10 grams per liter of wet emulsion of sodiummethacrylate.

WALTER J WEYER'IS.

of wet emulsion of sodium

